Genetic Information

Figure 5.4 Possible representations of the multidimensional space controlling gene regulation in eukaryotic cells. A, Individual genetic elements (black circles) interact with many other elements through positive and negative interactions (activation and repression arrows, respectively) quantitative aspects of these interactions are represented by variable thicknesses (strength of the interaction) and lengths (duration of the interaction) of the interaction arrows. B, As a concept diagram,...

Plants are used to having identity crises

Rolf rutishauser, valentin grob and evelin pfeifer Macroscopic nature is never really anomalous. Abnormalities, like other exceptional cases, at least show incontestably, what the plants can do. However, regardless of how much faith one has in anatomical definitions, they should not be taken as more than a means of communication prior to subsequent genetic analysis. Truth, except as a figure of speech, does not exist in empirical science. Our green and living world is a continuum in space and...

The Impact Of Evodevo On Evolutionary Theory

The conceptual framework of evo-devo arose as a response to the incompleteness of the neo-Darwinian synthesis (Callebaut et al. 2007). The paradigm of the synthesis was based on the correlation of phenotypic character variation with statistical changes of gene frequencies in populations. Adaptive change as a population genetic event was the explanandum. The paradigm of evo-devo, by contrast, represents a causal-mechanistic approach towards the explanation of phenotypic change in evolution. Here...

On comparisons and causes in evolutionary developmental biology

Denn mit dem Warum der Dinge kommt niemand zu Ende. Die Ursachen alles Geschehens gleichen den D nenkulissen am Meere eine ist immer der anderen vorgelagert, und das Weil, bei dem sich ruhen lie e, liegt im Unendlichen. For once you begin with the Why you can never get to the end. It is like the dunes by the sea, where behind each dune lies still another and the Because where you might come to final rest lies somewhere in infinity. Thomas Mann, Joseph und seine Br der Comparison is fundamental...

Unravelling body plan and axial evolution in the Bilateria with molecular phylogenetic markers

Jaume baguna, pere martinez, jordi paps and marta riutort setting the problem The emergence of dramatic morphological differences (disparity) and the ensuing bewildering increase in the number of species (diversity) documented in the fossil record at key stages of animal and plant evolution have defied, and still defy, the explanatory powers of Darwin's theory of evolution by natural selection. Among the best examples that have captured the imagination of the layman and the interest of scores...

Evolving body features

'Distinctive features', 'key apomorphies', 'novelties', 'innovations'. All these terms point to the fact that some characters in an organism are 'special' in some respect, and these have attracted the most interest from biologists and challenged the explanatory capacity of evolutionary theories. These are characters that emerged as new features during the evolution of a lineage, or that are believed to be the principal cause of a successful phyletic radiation. 'Evolution is tinkering' and in...

Arthropod appendages a prime example for the evolution of morphological diversity and innovation

Nikola-michael prpic and wim g. m. damen The morphology of the appendages of the arthropods has been adapted to a large number of life styles that is virtually unparalleled in any other organ in the Metazoa. Different appendage types exist e.g. for walking, swimming, jumping, prey-capture, chewing, biting, mating, egg-laying, breathing in air, fresh water and salt water, and sensory perception see Figure 20.1 for examples . Very specialised appendage types exist for specialised modes of life...

A pragmatic approach for selecting evodevo model species in amniotes

Athanasia c. tzika and michel c. milinkovitch One major classical justification of using a model metazoan species for experimentation has been that discoveries of biological phenomena in that species could be extrapolated to other multicellular species. Because the chances that this extrapolation is valid in humans depend on the phylogenetic distance between humans and the model species, many researchers have somewhat sacrificed the major benefits of small size, short generation time and ease...

Prospects of evodevo for linking pattern and process in the evolution of morphospace

Evolutionary developmental biology or evo-devo will make crucial contributions over the coming years to exploring the occupancy of mor-phospace. Why do species show the patterns of diversity and disparity they do, and to what extent do such patterns reflect the ways in which phenotypic variation is generated as well as the processes of natural selection Evo-devo in appropriate study systems is providing the means to explore fully how phenotypic variation is generated by the processes intrinsic...

Are transposition events at the origin of the bilaterian Hox complexes

The genome sequences of two non-bilaterian animals, the cnidarians NematosteUa vectensis and Hydra magnipapillata, have been recently completed. These new data lead to the fascinating result that the complement of Hox genes in the cnidarian ancestor is considerably lower than that in the bilaterians, although the complexity of their genome is otherwise similar Technau et al. 2005 . Thus, there is a correlation between the radiation of the Bilateria and the expansion of the Hox complex. In the...

Chiparian Planula

Bra. -cat. obi. chd gtc, bmp5-8 ash Figure 12.4 Comparative axial expression, in a simplified form, of key developmental genes between cnidarians planula larva, top left, and polyp, bottom left and bilaterians right . In the planula larva genes expressed asymmetrically along the directive axis 'D-V' axis are also depicted. A anterior AB aboral D dorsal O oral P posterior V ventral. 'D' and 'V' imply the likely, but still undefined, DV character of the directive axis in...

References

Analogy in the history of science. In M. F. Ashley Montagu ed. Studies and Essays in the History of Science and Learning, Offered in Homage to G. Sarton. New York Henry Schuman, pp. 221-233. Arber, A. 1950. The Natural Philosophy of Plant Form. Cambridge Cambridge University Press. Baluska, F., Volkmann, D. amp Barlow, P. W. 2004. Cell bodies in a cage. Nature 428, 371. Barlow, P. W., Luck, H. B. amp Luck, J. 2001. The natural philosophy of plant form cellular autoreproduction...

Conflicting hypotheses on the nature of megaevolution

Parasitic Platyhelminthes

Here is a question of the utmost importance for our understanding ofwhat has been called the 'big picture' of evolution Simpson 1944,1953 are the divergences that lead ultimately to high-level sister groups, such as those that would typically be labelled as orders, classes and phyla, qualitatively or quantitatively different from those that lead to low-level sister groups, such as races, species and genera In other words, is megaevolution more than just accumulated micro macro-evolution, or...